1. Field of the Invention
The present invention relates to an improved biopsy instrument and more particularly to a medical instrument that permits a clean margin core of tissue to be obtained with the physician using one hand to control the instrument.
2. Description of the Prior Art
In performing procedures for obtaining tissue samples, there have existed problems in obtaining diagnostic material adequate for definitive interpretation by a qualified pathologist. Using the case of obtaining samples of tissue for the diagnosis of malignancies of the prostate gland as an example, it is known to utilize cytologic studies based on a fine needle aspiration biopsy. For example, a device for this purpose is disclosed in U.S. Pat. No. 3,595,217 to Rheinfrank. A hollow biopsy needle is passed through a guide tube attached to the operator's finger which is placed on the prostate gland. The needle penetrates the gland and a syringe attached to the needle withdraws a tissue sample. Unfortunately, the use of an aspirating needle to obtain samples from the prostatic tissue has not, in general, produced satisfactory diagnostic material and this approach has been largely abandoned in the United States.
Consequently, a preferred approach is to obtain a core sample. Many physicians utilize a biopsy needle available from Travenol Laboratories, Inc. of Deerfield, Ill. and described in U.S. Pat. No. 3,477,423 to Griffith. The Travenol TRU-CUT.sup.R biopsy needle comprises a hollow tubular cutting cannula having a sharpened distal end attached to a plastic handle. A coaxial solid stylet telescopes within the cannula and is attached to a knob at its proximal end. The distal end of the stylet is sharpened and includes a transverse slot or specimen notch adjacent to the sharpened end.
In the prostatic sample example, the physician positions the stylet of the Travenol needle to project slightly from the cannula. The index finger of one hand is placed along the cannula with the tip in contact with the stylet distal end and the handle is held in the palm. Approaching the prostate gland transrectally, the gland is explored with the finger tip to locate a nodule or suspicious area. After locating a point for a sample, the needle is cased forward into the nodule. Once in place, the stylet is plunged to the desired depth.
The physician must then remove his hand and finger, grasp the stylet knob in one hand, and push the cannula handle forward with the other hand. Theoretically, the cutting end moves along the stylet and severs a sample of tissue projecting into the transverse slot in the tip of the stylet. The entire needle is then withdrawn from the gland and the sample removed from the stylet.
In practice, the manipulation of the cannula during this latter step is quite difficult since the tip of the stylet is embedded in the soft and pliable prostatic tissue several inches from the handle. The stylet knob gives very little steady support to the needle assembly and the stylet tip, due to its smaller diameter, penetrates the tissue somewhat easier than the tubular cannula cutting edge. On occasions, when attempting to push the cannula into the tissue, the entire needle moves forward, puncturing the bladder or uretha. It is also common to attempt to move the cannula forward only to have the stylet back out of the tissue. When this occurs, the physician must remove the needle, reposition the stylet, and try again.
Since the procedure involves puncturing of the colon wall, each attempt increases the risk of infection. Most physicians limit such attempts to two or three passes. Even with a successful insertion of the cannula, the instability of the Travenol needle often results in a limiting core sample. Similar problems exist in obtaining biopsies of other organs.
Other biopsy devices are known. For example, Russian Pat. No. 400,319 teaches a needle having an adjustable depth device and obtains a sample by suction. Drer, European Pat. No. 10,321 discloses a one-handed instrument suitable for taking a biopsy of yieldable tissue using a spring driven cannula. Baumgartner in U.S. Pat. No. 4,396,021 describes a biopsy instrument designed to be inserted into a standard cystoscopic instrument and must be guided visually.
In my co-pending application, Ser. No. 579,158 entitled "Transrectal Biopsy Device", I disclose an improved instrument of the Griffith-type which permits the physician to guide the needle to the exact point required for a sample by means of a guide tube and to thereafter maintain that hand and finger in place during the remainder of the sampling procedure, eliminating the problems in using the Griffith-type needle noted above.
In that invention, the operator can accurately and safely perform the sampling procedure. However, the unit requires the use of one hand to hold the needle in position and the other hand to operate the stylet and cannula for obtaining a sample of tissue. It is desirable that the sampling procedure be accomplished using the same hand holding the instrument in place. Thus, the other hand of the physician is free to steady the patient during the critical sampling period.
Thus, there is a long-felt and unfilled need for a biopsy needle which can be guided to the required point of the prostate gland by the physician's finger, a sampling stylet inserted, and a cutting cannula plunged forward without removal of the finger and which would permit the entire procedure to be completed using one hand.